Thoughts on the evolution of wireless networks and mobile web 2.0

Providing Internet Connectivity For Meetings - Do's and Don'ts

One of the major pain points when attending international meetings with more than just a few attendees these days is more often than not the lack of proper Internet access at the meeting venue. When those meetings take place in hotels, some organizers just rely on the hotel's Internet connectivity, which is often unable to provide proper service to more than a few people simultaneously. Often, connections are slow and sometimes the whole network becomes completely unusable as its breaking down once a critical number of simultaneous connections is reached.

Why Connectivity?

Some people might think connectivity during meetings and conferences is a luxury. That's not the case, however, as at least during the meetings I attend, participants require access to information in their home network, they need to communicate with other people during the meeting via email, instant messaging, etc. to get advice, use cloud infrastructure to exchange documents in real time with people on-site and off-site, they use connectivity for multi-user screen sharing, etc. etc.

Doing it On My Own With Cellular Backhaul

When recently hosting a meeting with 40 participants myself, I decided to not only rely on an external party to provide adequate Internet connectivity but to gain some experience myself. I therefore set up my own local Wi-Fi network and provided backhaul capacity over a high speed broadband cellular network in Germany. Perhaps a somewhat risky plan but with achievable cellular speeds in the double digit MBit/s range I thought it was worth a try. I spent many evenings putting the required kit together and trying out things as before as during the meeting there is hardly any time for experiments. It either works out of the box or you have a problem. To my delight the network I provided worked exceptionally well with participants having been very happy about the overall experience. Understandably, I was very pleased not only about this but also about the experience and insight I gained. The following is an account of the thoughts that went into this, the equipment used and the lessons learnt in case you might plan a similar thing in the future.

Getting the Wi-Fi right

One of the first bottlenecks frequently encountered is that there is often only a single Wi-Fi channel available at a meeting site. While in theory even an 802.11g channel has a capacity of 54 MBit/s in practice, this is reduced to just about 22 MBit/s in the best case, which is a single device communicating with an access point only a few meters away. With several dozen devices not in close proximity communicating with the access point simultaneously this value further drops to a much lower value.

The solution to this is to use several Wi-Fi several access points even in a single room and assign them different frequency channels and SSIDs. It's also a good idea to use the 5 GHz band in addition as there is little interference on that band today. Not all devices support this band and if that access point uses a separate and "interesting" SSID such as "fastest channel" those participants who can see it will likely use it, thus enjoying superior speeds and at the same time removing their load from the 2.4 GHz channels.

Another important thing is to make sure that in case the meeting has dedicated Wi-Fi resources, the channels used do not partly or fully overlap with other Wi-Fi access points in the area if at all possible. On the 2.4 GHz band, Wi-Fi's need to be 4 channels apart from each other. There are tools such as "Wlaninfo" on Windows or a nice command in Linux such as "sudo iw dev wlan0 scan | grep -w 'channel\|SSID\|signal'". Things still work if the channels overlap or are stacked on top of each other but throughput is reduced to some degree depending on how much load there is on the other access point.

The first thing that usually goes on the local Wi-Fi is often not the notebooks but the smartphones of the participants. Roaming charges remain expensive and the local Wi-Fi is a welcome relief. But despite the devices being small and the amount of data transmitted being perhaps low, the number of UDP / TCP connections that need to be translated by the NAT is by no means lower than that of a notebook. So beware, a smartphone counts as a full device and on average, 1.5 devices should be put in the calculation per participant.

Which brings me to Wi-Fi compatability. Most devices today are tested for Wi-Fi compatability. In practice, however, I've seen it more than once that an 802.11n capable smartphone has brought an 802.11n access point to its knees due to some sort of incompatability. In other words, all other users of that channel suddenly can't communicate anymore either. For the moment, the best solution to this is to switch off 802.11n support in the access point or only use 11n in the 5 GHz band. This way, only one of the channels is impacted and most people will not notice or switch to another channel once things start to go wrong.

Local Networks and Hords of Devices

Another issue I have encountered is that some local networks run out of IP addresses because their DHCP server is limited to just a few dozen IP addresses in the first place or becasue they only use a single /24 subnet with 256 addresses for the whole hotel or meeting complex. Even if there are fewer people there at any one time, the DHCP server might run out of IP addresses as these are usually assigned for a full day and even when devices sign-off the IP addresses remain assigned until the lease runs out.

And yet another issue that seems to make life difficult at meetings with many participants is that the local infrastructure is unable to cope with the massive number of simultaneous TCP and UDP connections the local backhaul router has to perform Network Address Translation (NAT) on. This is necessary as local networks usually assign local IP addresses and only use a single global IP address for all participants. That can work quite o.k. but the local equipment needs to be able to handle the massive number of simultaneous connections. In business meetings one thing comes to help: Most participants use VPN tunnels which hide the TCP and UDP connections to the company network or even all connections of the device from the local network. Thus, instead of dozends or hundres of translations, the local NAT only has to handle a few for such a device.

How Much Backhaul Bandwidth

And finally, one of the crucial things is how much backhaul bandwidth to the Internet is available. For a meeting of 50 to 100 participants, 10 MBit/s in the downlink direction and at least 3-5 MBit/s in the uplink direction is a good ballpark number. Any less and congestion is likely to occur. More is better, of course...

What To Ask the Hotel or Internet Provider

In case you plan to use the Internet connectivity provided locally, ask the hotel or Internet provider about the things mentioned above. If they can't come up with good answers or just make general promisses, chances are high it won't work well in the end. And one more important thing: On-site support is vital as in case things go wrong as meetings can go sour instantly when connectivity has broken down.

Part 2 - How To Do It Yourself

The above should already be pretty good advice in case you decide to provide your own network infrastructure and backhaul. In the second part, I'll go into the details into the equipment and software I used and the experiences gained with it.